sryanbruen Registered User
#1

After one of the weakest La Nina events on record, the models immediately turned around to an El Nino situation in 2017/18. Up to February, the models were showing a moderate El Nino and as I already said in the La Nina thread here:

http://www.boards.ie/vbulletin/showpost.php?p=102739020&postcount=21

Moderate El Nino is a good sign of a cold or blocked Winter but there is still a chance for a mild and wet Winter as with Ireland's weather, there is never a guarantee .

The CANSIPS model is showing a super strong El Nino to take place in 2017/18 but that's only two years after the previous super strong El Nino. There have been only three super strong El Nino events in existence so far. These being:

  • 1982/83
  • 1997/98
  • 2015/16

There is a long gap in between each of the above but how the CANSIPS is expecting a super strong El Nino to take place just two years after the previous one is very remarkable.

What's interesting to point out is the fact that each of the super strong El Nino events above had a remarkably mild Winter month with January 1983, February 1998 and December 2015. Obviously, January 1983 wasn't as extreme as the latter two but it was still very remarkable how mild it was.

We have not had a moderate El Nino since the beautiful Winter of 2009/10.. . It'd be amazing if we got a moderate El Nino this Winter and have a repeat of that Winter BUT we can all care to dream .

I think the CANSIPS is going way overboard with the super strong El Nino. I don't think it will come off and the most I can expect right now is a moderate El Nino. But hey, just because I don't think it will happen doesn't mean it won't happen.

God love us if it's a super strong El Nino and we have to suffer a month like December 2015 again .

EDIT: Also, it looks as though the cold blob in the Atlantic that has been stuck there since late 2014 will continue through 2017 which will make a negative NAO very difficult to happen. To add some optimism, the cold blob does not look nearly as cold or as large as it was in 2015, so very low chance we will get a month as wet as December 2015 next Winter.... at the moment that is from what I see.

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sryanbruen Registered User
#2

UPDATE: The signal is still very strong for an El Nino to take place during the course of 2017/18. The strongest signal is for it to a moderate El Nino.



Please to God don't be a super strong El Nino again!



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sryanbruen Registered User
#3

UPDATE: A moderate El Nino is still on the cards as predicted by the CFSv2 but the general consensus is quite close to a strong El Nino.



I've gathered some reanalysis here on Winters with a moderate & strong El Nino in regards to 500mb height anomalies.

Here is the reanalysis for Winters with a moderate El Nino:



This reanalysis shows that a moderate El Nino is a great contender for cold winters as the jet stream according to the low pressure distribution is on a very southerly track down towards the Mediterranean and with plenty of northern blocking, very stubborn northern blocking I should say. This northern blocking builds into parts of the UK and Ireland. This reanalysis shows a huge possibility for a cold Winter in 2017/18 if a moderate El Nino were to come off. Northerlies would not be able to take place in this pressure distribution as you would need a build of high pressure to center more towards Greenland and low pressure over Scandinavia. This reanalysis shows that easterly winds would be very evident through the Winter, something some of us have been wanting for so long!

But regardless of saying all this, you can't guarantee a cold Winter with a moderate El Nino as evident from Winter 1987/88 or Winter 1991/92 or Winter 2002/03. Let's just hope that if a moderate El Nino does take place, the NAO will go very negative and the QBO will become an easterly.

Meanwhile, here's the reanalysis for strong El Nino winters (not counting very strong El Nino winters like 1982/83, 1997/98 or 2015/16):



In contrast with the moderate El Nino reanalysis, this reanalysis shows a very awful pattern. The reanalysis shows some northern blocking but way over to Canada and western Greenland along with a very deep area of low pressure extending from northern Russia all the way to Mexico with Ireland included in this. In fact, Ireland is centered near one of the places where the low pressure is at its worst. It's clearly evident here that a strong El Nino is most certainly not a good sign for a cold Winter, far from it actually. Instead, a very stormy Winter could well take place if a strong El Nino were to take place. There has not been a strong El Nino since 1972/73, so we're overdue a strong El Nino at this stage and given how dry this past Winter was, we're due a very stormy Winter I think.

These are only predictions based on previous occurrences of moderate and strong El Ninos, not in any way a guarantee.

Reanalysis charts sourced from https://www.esrl.noaa.gov/psd/cgi-bin/data/composites/plot20thc.v2.pl

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sryanbruen Registered User
#4

I found this interesting graph today which shows the NAO for December to February (Meteorological Winter) from 1900 to 2012 or Winter 1899/1900 to Winter 2011/12.



Out of the moderate El Ninos that have been recorded, a negative NAO has occurred during Winter 2009/10, Winter 2002/03 (though very weak negative NAO), Winter 1987/88 and Winter 1963/64. So this means that a negative NAO has taken place in all moderate El Nino winters since 1963 with the exception of 1988/89 and 1991/92.

If a moderate El Nino were to take place, we would have a 66% chance of a negative NAO to take place. Therefore, that means 34% chance of a positive NAO to take place. So with a moderate El Nino, it is much more likely for a negative NAO to happen than a positive one which is good for cold winters.

The graph shows that Winter 2009/10 had the most negative NAO within the last 100 years which is very interesting and Winter 1962/63's NAO is the 3rd most negative.

I'll hopefully find the AO for the same period as this graph represents with the NAO. Let's hope there is some good correlation once I do though I'd highly doubt that knowing our climate never has any guarantees and will always surprise us with exceptions to our theories .

NAO graph sourced from: https://www.rmets.org/sites/default/files/abstracts/Mar/16032013-burt.pdf

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sryanbruen Registered User
#5

The latest SST anomaly chart here from NOAA shows temperatures in the ENSO region up to the standard of a very, very weak El Nino (or maybe neutral?) though the ENSO region in the eastern Pacific has temperatures up to the standard of a super strong El Nino with anomalies of over +5.0c. Due to the northern Pacific being much colder than it has been in recent years since like Winter 2012/13 along with the rather uneventful temperatures in the rest of the ENSO region bar the eastern Pacific, I think the chart is indicating neutral conditions once you consider all these. The NAO is looking quite positive given how cool the north Atlantic still is, that annoying cold blob is still not gone!



Here's the SST anomalies for this time last year. As you can see, the super strong El Nino became a rather moderate to strong El Nino by March 2016. It's also interesting to point out that the northern Pacific was also quite cool, like now in 2017 along with the northern Atlantic being very cold which meant that the NAO was very positive.



It's funny to find this NAO index and anomaly chart from 2015/16 now like it's showing that the NAO was going to super negative like 2010 standard NAO during the middle of January 2016 , ah god nobody knew what was around the corner.... 15c during the day and 10-12c at night for Christ sake . I just came across this and wanted to show it 'cause it's so funny looking back on this.



Here are all the such charts of the SST anomalies for this period of time before recent moderate El Ninos to compare with the current one:



There was no sign of a moderate El Nino in March 2009 around this period of time interestingly. The Pacific was firmly in a La Nina type setup.



Mmmm, there was no sign of a moderate El Nino in March 2002 either . It'd be interesting to see if the models were predicting a moderate El Nino during those years but unfortunately, I cannot find out that.

The confidence of a moderate El Nino to take place by the CFS v2 is still high.

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sryanbruen Registered User
#6

The CFSv2 continues to show confidence of an El Nino to take place during 2017 and into 2018 but confidence of a moderate El Nino has now been downgraded to a weak El Nino. Beware that there are still a good few ensembles going for a moderate El Nino but from what the general consensus is showing, they're outliers.



As a result of this, I gathered this pressure reanalysis on Weak El Nino winters. The reanalysis shows some intense northern blocking which is normally required for a cold Winter like 2009/10 or 1962/63. However, there is a deep trough over much of Europe including the UK and Ireland. Like strong El Nino winters, this is pretty straightforward. With this setup if we do get a weak El Nino, expect a very stormy Winter like 2006/07 (which had a weak El Nino) or 1994/95. Again I say though, with Ireland's weather, you can never guarantee anything. This reanalysis however shows that a weak El Nino is a very good sign for a stormy Winter.



What about the summers that followed the weak El Ninos? Well here's the pressure reanalysis of the summers that followed those weak El Nino winters. The reanalysis again shows very stubborn and intense northern blocking with a trough to the south of the UK and mainland Europe. This looks like a very cool and poor Summer setup to me. I like to compare this setup to Summer 2015. Summer 2015 had northern blocking and a trough right over us with high pressure over the continent. This gave us a very cool Summer. However, the trough is more over Europe this time. So should we expect a somewhat more settled Summer in 2018 (if a weak El Nino comes off) than 2015 with the slightly different setup?



The temperature reanalysis here of the same summers, however, shows that temperature anomalies are around average in Ireland with any cold temperatures more towards the southeast of England. Also, temperature anomalies look slightly above average to the west and northwest of Ireland. This is a weird distribution of temperature anomalies . The pressure reanalysis shows the potential for a poor Summer whilst the temperature anomalies show it as a very benign Summer. I would also like to point out that Summer 1995 is included here, as it followed the weak El Nino of 1994/95 (which was a very stormy and wet Winter). Summer 1995 is a bit weird here because it was much different than what the reanalysis shows. Goes to show ya that reanalysis doesn't tell you everything!

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sryanbruen Registered User
#7

With the warming towards the eastern ENSO region near Peru weakening, a weak El Nino looks the most likely event to take place. The CFSv2 like I said a few days ago has downgraded to a weak El Nino. The PDO (Pacific Decadal Oscillation) is around neutral but I expect this to become more positive as time goes by due to the negative SST anomalies. With a positive PDO, a weak El Nino is possible but any El Nino conditions that will try to get designated across the ENSO region will have a very tough time to do so.

The super strong El Nino of 2015/16 was helped a lot by the PDO being very negative (therefore, SST anomalies being very positive). However, this time with the PDO positive, it will make the El Nino very difficult to get designated.

A weak El Nino is normally characterised by the following (though again, no El Nino or La Nina is exactly the same of their effects so take these with a pinch of salt) for Ireland:

  • One of the Summer months preceding the weak El Nino Winter should be very warm especially across the UK (for example, June/July/August 1976, July 1994, August 2004 and July 2006)
  • One of the Autumn months preceding the weak El Nino Winter should be very mild (like the Summer months) (for example, September 2006, November 2004 and November 1994)
  • The winters with the weak El Nino are normally mild (you have to go back to the 70s for a cold Winter with a weak El Nino)
  • Some of the summers that succeed weak El Nino winters are some of the best summers (like 1969 and 1995. But this is not always the case as Summer 1954 followed the weak El Nino Winter of 1953-54 and Summer 1954 was very poor)


A weak El Nino does not that have many characteristics for Ireland and is more like a trial and error for guessing what effects it will have on Ireland.

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sryanbruen Registered User
#8

The El Nino continues to be downgraded by the CFSv2. The CFSv2 is now on the borderline between weak El Nino and ENSO neutral.

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pedigree 6 Registered User
#9

sryanbruen said:
The El Nino continues to be downgraded by the CFSv2. The CFSv2 is now on the borderline between weak El Nino and ENSO neutral.


I wonder does this mean a serious drought this year goes from possible to probable?

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sryanbruen Registered User
#10

Very little change since I last posted here. The CFS is still showing the possibility of a borderline weak El Nino/ENSO neutral event later this year. Feel free to change the title of the thread mods because the title at this stage could be considered clickbait .

sryanbruen Registered User
#11

I think it's safe to say that it will most likely not be an El Nino Winter in 2017/18. The CFSv2 has now downgraded it to an ENSO neutral Winter albeit still a lot of outliers going for an El Nino event.

sryanbruen Registered User
#12

pedigree 6 said:
I wonder does this mean a serious drought this year goes from possible to probable?


Looks to be that way.

The CFSv2 is now predicting ENSO neutral as we go into 2018, well the consensus is. Some ensembles are still going for an El Nino event.

sryanbruen Registered User
#13

Despite the CFSv2 showing ENSO neutral at this stage, the Jamstec is still going for a moderate El Nino and the ECMWF is going for a weak El Nino. Still a lot of uncertainty, even at this stage.

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